This invention relates to electromagnetically operated valves, and more particularly to an improved solenoid valve having coaxial armatures in which only one coil is necessary.
Three-way solenoid valves are known and have been used to control fluid flow, including gaseous fluid flow. For example, U.S. Pat. No. 5,218,996 discloses a solenoid valve having three operating positions for the purpose of rendering the system more efficient when regulating fluid pressure. The disclosed solenoid valve has inner and outer coaxial coils and first and second coaxial armatures. A first ball valve is secured to and movable with the first armature, and a second ball valve is secured to and movable with the second armature. A first compression spring urges the first armature downward into a position wherein the first ball valve normally closes an exhaust port. A second compression spring urges the second armature downward into a position wherein the ball valve is open. When one of the coils is energized, the first armature moves against the resistance of the first compression spring to open the first valve. The independent armatures allow only one of the valves to be open at a given time, but allows both valves to be closed at the same time.
U.S. Pat. No. 4,619,289 describes another solenoid-controlled valve that is said to be capable of achieving changeover and control at three positions by exciting only one particular solenoid. The solenoid has first and second coaxial armatures or members. The armatures are independently moveable along the axis via a solenoid coil.
While the previously known solenoid valves are useful for the purposes for which they are described, there is still a need for a valve having built-in sealing redundancy, which is particularly useful, desirable and required in low-pressure/high-pressure fluid applications.